Chemodivergent C(sp3)–H and C(sp2)–H cyanomethylation using engineered carbene transferases

Abstract

The ubiquity of C-H bonds presents an attractive opportunity to elaborate and build complexity in organic molecules. Methods for selective functionalization, however, often must differentiate among multiple chemically similar and, in some cases indistinguishable, C-H bonds within the same molecule. An advantage of enzymes is that they can be finely tuned using directed evolution to achieve control over divergent C-H functionalization pathways. Here, we present engineered enzymes that effect a new-to-nature C-H alkylation (C-H carbene insertion) with unparalleled selectivity: two complementary carbene C-H transferases derived from a cytochrome P450 from Bacillus megaterium deliver an α-cyanocarbene into the α-amino C(sp 3 )-H bonds or the ortho-arene C(sp 2 )-H bonds of N-substituted arenes. These two transformations proceed via different mechanisms, yet only minimal changes to the protein scaffold (nine mutations, less than 2% of the sequence) were needed to adjust the enzyme's control over the site-selectivity of cyanomethylation. The X-ray crystal structure of the selective C(sp 3 )-H alkylase, P411-PFA, reveals an unprecedented helical disruption which alters the shape and electrostatics in the enzyme active site. Overall, this work demonstrates the advantages of using enzymes as C-H functionalization catalysts for divergent molecular derivatization.

SiO2 assisted Cu0–Cu+–NH2 composite interfaces for efficient CO2 electroreduction to C2+ products

“…The high coverage of *H ad species can enhance the protonation process of C 2+ intermediates and desorption of products, thus promoting the efficient formation of C 2+ products from the CO 2 RR process. 50,51 According to the above analysis results, the CO 2 RR mechanism on the surface of Cu 2 O@SiO 2 -NH 2 can be reasonably proposed (Fig. 7d).…”

Synthesis of Trifluoromethylated Monoterpenes by an Engineered Cytochrome P450

“…[13] P411-PFA has been further engineerd to catalyze the cyanocarbene transfer reaction of 4-phenylmorpholine and N-substituted arenes analogs recently. [16] The progress in engineering P450BM3 to catalyze non-native reactions demonstrates its catalytic versatility and potentially substrate promiscuity, [17] which provides the possibility for further exploitation of P411-PFA to expand the substrate scope and derivation of natural monoterpenes. Initially, ethyl diazoacetate was selected as the model carbene donor rather than the gaseous CF 3 CHN 2 for the simplicity of the experiment setup.…”

Carbene Radicals in Transition-Metal-Catalyzed Reactions

“…Recently, the group of Arnold reported a series of efficient carbene transfer reactions using engineered heme-type Fe enzymes (Scheme 5 D). 46 Expanding on computational work by Sharon et al, the carbene intermediates involved in these reactions were proposed to be carbene radicals based on DFT studies. 49i The presented experimental data, however, all point to electrophilic Fischer-type carbene reactivity.…”